This invention relates to an optical module, and particularly to an optical communication transmission or reception module.
Coaxial type transmission or reception optical modules installed in XFP (10 Gigabit Small Form Factor Pluggable) or other optical transceivers are classified into those for Telecom (telephone system) applications covering a communication distance of 10 km to 40 km and those for Datacom (data communication) applications covering a communication distance of 220 m to 10 km.
Optical modules for Telecom applications are required by related standards to have an internal reflection attenuation of 27 dB or higher. In order to satisfy this requirement, some related optical modules for Telecom applications are designed such that the optical axis of a sleeve inserted into one end of a ferrule holding an optical fiber is offset from the optical axis of a lens portion of an optical element mounted at the other end of the sleeve. This type of optical module is described in Japanese Laid-Open Patent Publication No. 2008-292676, for example.